How to develop a AGC circuit for a GPS IC in a discrete form

[brmadhukar]

Gain control Circuit

Hi,
I need to develop a AGC circuit for a GPS IC, in the discrete form. The traditional method of using the carrier power to to provide feedback cannot be done due to low power. I have to implement it by using the ADC outputs, the second significant bit being the reference. it should be maintained high for 30% of the time. This can be achieved using current sources charging and discharging a capacitor. If this is the only "analog" way of doing is the circuit feasible. If not what are the other methods of doing it. Using digital control it is easy and I have already accomplished it.

TIA
Madhukar

 

[AL0117]

Re: Gain control Circuit

Hi,

Take a look at the AD8313 and AD8314 from Analog Devices, they are RF detectors, but they can be used in controller mode.

Regards, Al

 

[brmadhukar]

Re: Gain control Circuit

Hi,
I forgot to add that the IF is differential at 15.42MHz so the AD amps do not really serve the purpose. May be there is a power detector that works at this frequency.
BR
Madhukar

 

[AL0117]

Re: Gain control Circuit

one more : could you try SA614 from Philips for detector. It can be used up to 21.4 MHz IF, and the RSSI output has a wide dynamic range

regards, Al

 

[amihomo]

Hi

what is the relation between "response time" and "video bandwidth" of an RF detector such as AD8314 ?